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Extensive Journal of Applied Sciences
Available online at www.ejasj.com
©2014 EJAS Journal-2015-3-2, 39-43
ISSN 2409-9511
The Effect of Solar Radiation and Temperature on
Solar cells Performance
Davud Mostafa Tobnaghi* and Daryush Naderi
Sama technical and vocational training college, Islamic Azad University, Parsabad Moghan Branch, Parsabad
Moghan, Iran
Corresponding author: Davud Mostafa Tobnaghi
ABSTRACT: In this paper, the performance and overview use of solar cells is expressed. The role of
several of operation condition such as temperature, sunlight intensity and the solar panel installation
location on the solar cells output parameters has been studied. Experimental results the amount of
solar cell output parameters variations such as maximum output power, open circuit voltage, short
circuit current, and fill factor in terms of temperature and light intensity shows. The best performance
of solar panels in sunny and cold day has been suggested and also suitable orientation and tilt of solar
panels has been determined. Obtained results could lead to optimal use of solar panels.
Keywords:solar cells, temperature, light intensity, tilt, orientation
INTRODUCTION
Nowadays we get approximately 80% of our energy from non-renewable energy sources, e.g. fossil fuels.
Pollutants and greenhouse gases increase when fossil fuels are converted into electricity or heat. Therefore
atmosphere is damaged and global warming developed. Fortunately, as the resources are limited, our
dependence on fossil is close to its end. Presently, the world annual energy consumption is 10 terawatts (TW)
and by 2050 this amount will be about 30 TW. The world will need about 20 TW of non-CO2 energy to stabilize
CO2 in the atmosphere by mid-century. The simplest scenario to stabilize CO2 by mid-century is one in which
photovoltaics (PV) and other renewable are used for electricity (10 TW), hydrogen for transportation (10 TW),
and fossil fuels for residential and industrial heating (10 TW) [1]. Thus, PV systems will a significant role in the
world energy supply in the future.
Photovoltaic systems have been installed to provide electricity to the billions of people that do not have
access to mains electricity. Power supply to remoter houses or villages, irrigation and water supply are important
application of photovoltaics for many years to come. In the last decade, PV solar energy system has shown its
huge potential. The amount of installed PV power has rapidly increased. Nowadays, nearly 70 GW of PV power
are installed worldwide. Perhaps the most exciting new application has been the integration of solar cells into the
roofs and facades of buildings during the last decade.
Solar cells are based on semiconductor materials. semiconductor are materials from either group IV of the
periodic table, or from a combination of group III and group V, or of combinations from group II and group VI.
Nearly 80% of cells on the market are crystalline silicon based cells. The characteristics of silicon solar cells are
affected on changing the environment. In this paper, some of the environmental effects that degrade the
properties of solar cells are discussed. The presence of dust on the surface of the solar cells deteriorates their
performance [3]. Concentration of dust and velocity of wind and cloudy days also reduces the current and power
of solar cells. Solar cells are exposed to temperatures changing from 5 to 50 0c. The output parameters such as
open circuit voltage, fill factor, short circuit current and efficiency of the solar cells are temperature dependent.
The sun radiates in all regions of spectrum, ranging from radio waves to gamma ray. Our eyes are sensitive
to wavelengths ranging from 400-700 nm. In this narrow range, called visible range, the sun emits about 45% of
total radiated energy. The orientation and inclination of the photovoltaics panel and Geographical location of the
mounting panel determine the amount of sun irradiation that the panel surface receives.
SOLAR CELL OPERATION
The photovoltaic (PV) effect is the direct conversion of light into electricity in solar cells. When solar cells are
exposed to sunlight, electrons excite from the valence band to the conduction band creating charged particles
called holes. In one PV cell, the upper or n‐type layer is crystalline silicon doped with phosphorus with 5 valence
electrons while the lower or p‐type layer is doped with boron, which has 3 valence electrons. By bringing N and
Ext J App Sci., 3 (2): 39-43, 2015
P type silicon (semiconductors) together, a p-n junction serves for creating an electric field within the solar cells,
which is able to separate electrons and hole and if the incident photon is energetic enough to dislodge a valance
electron, the electron will jump to the conduction band and initiate a current coming out from the solar cells
through the contacts [2]. Figure 1 shows this process.
Fig 1. solar cells working principle
A. I‐V Characteristics of Solar Cells
The equivalent circuit of the solar cells is combination of a current source (light generated current) and a
diode. Solar cells behave similarly to diodes and thus the electrical characteristics of solar cells represented by
using current-voltage curves (I‐V curve). Figure 2 shows the I‐V characteristics and the equivalent circuit of solar
cells.
Fig 2. (a). equivalent circuit. (b). I‐V curve of solar cells
Isc represents the short circuit current, at which the current is at maximum and where voltage is zero. V oc is
open circuit voltage, at which the voltage is maximum and where current is zero. The maximum power P max
produced by a solar cell is reached when the product I‐V is maximum. This can be shown graphically (fig. 2.b)
where the maximum power point represents the largest rectangle area under the IV curve [3].
Output current and open circuit voltage of a solar cell is given by the following relations:
qv
 nkT


I  I L  I 0  e  1


VOC 
nkT  I L 
ln  
q
 I0 
(1)
(2)
Where k is the Boltzmann constant, T is the temperature in terms of Kelvin, q is Electric charge, V is output
voltage of solar cell, IL is light generated current, and I0 is the reverse saturation current.
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Ext J App Sci., 3 (2): 39-43, 2015
EFFECT OF OPERATION CONDITION
A. Effect of Temperature
The one sample of the commercially solar cells is used for experimental measurements. The solar cell was
fabricated mono-crystalline structure with using phosphorus diffusion into a p-type silicon wafer.
Voltage-current (I-V) characteristics and output parameters of solar cell was measured. To obtain of solar
cell I-V characteristics, sample was illuminated by reflective lamp with Light intensity equal 1000 W/m 2. The
measurements were performed at 15, 25, and 50 0c temperature with highly accurate measuring equipment at
the institute of Radiation Problems of Azerbaijan National Academy of science. Voltage-current characteristics of
sample have been showed in figure 3.
I mA/cm2
35
30
25 °C
25
15 °C
20
50 °C
15
10
5
0
0
200
v mv
400
600
Fig 3. V-I characteristics of solar cell affected by temperature
Increases in temperature reduce the band gap of a solar cell, whereby effecting the solar cell output
parameters [4, 5]. The parameter most affected by temperature is VOC . The open-circuit voltage decreases with
temperature due to the temperature dependence of the reverse saturation current.
2
Dni
I 0  qA
LN D
(3)
Where D is the diffusivity of the minority carrier given, L is the diffusion length of the minority carrier, N D is
the doping, q is the electronic charge.
In the above equation, the most significant effect is due to the intrinsic carrier concentration (𝑛𝑖 ). lower band
gaps giving a higher intrinsic carrier concentration so higher temperatures results the higher𝑛𝑖 .
From figure 3, output and fundamental parameters of solar cells like maximum output power (𝑃𝑚 ), fill factor
(𝑓𝑓), short circuit current (𝐼𝑠𝑐 ), and open circuit voltage (𝑉𝑜𝑐 ), can be extracted. Table 1 shows the output
parameters of solar cell sample at different temperature.
Table I .Output parameters of solar cell sample in different temperature
temperature
(oc)
VOC
[mv]
ISC
[mA/cm2]
Pm
[mw]
FF
15
540
31.99
8.05
0.575
25
50
520
32
8
0.56
470
32.01
7.87
0.545
According to results, for silicon solar cells reduction in the open-circuit voltage is about 2.2 mV/°C. The shortcircuit current increases slightly with temperature, for silicon solar cell this is about 0.0006 mA/°C. FF decreases
with increasing temperature, for silicon solar cells this is approximated by 0.0015 per centigrade e. Also the effect
of temperature on the maximum power output is menus 0.005 mw/°C.
B. Effect of Light Intensity
In the figure 4, the V-I characteristics of previous sample at light intensities 1000, 800, and 500 w/m 2 have
been shown. As can be seen, V-I characteristics of solar cell vary under different levels of illumination.
41
I mA/cm2
Ext J App Sci., 3 (2): 39-43, 2015
35
30
25
20
15
10
5
0
1000 w/m2
800 w/m2
500 w/m2
0
100
200
300
v mv
400
500
600
Fig 4. V-I characteristics of solar cell affected by temperature
Variation of the light intensity incident on a solar cell changes all solar cells parameters. The light generated
current is proportional to the flux of photons therefore 𝐼𝑠𝑐 is directly proportional to the light intensity [6], While,
open circuit voltage increases logarithmically with light intensity, as shown in the equation below;
V 'OC  VOC 
nkT
ln X
q
(4)
V
Where OC is open circuit voltage at light intensity equal to 1000 w/m 2, X is the concentration of sunlight, for
example, when solar cells illuminated under 800 w/m 2, X equal to 0.8.
C. Effect of installation location, orientation, and tilt of solar cells
The orientation and tilt of the photovoltaic panels determine the amount of light intensity that the panel surface
receives. If the panels installed in northern hemisphere, they must be oriented facing south side, also facing north
in the southern hemisphere. In regions near the equator, the orientation is not considerable but a minimum of 10
degree tilt is necessary for that evacuate water in rain condition. The optimum tilt angle of panels depends on
installation location. As a general rule, Tilt of panels should be equal to the latitude minus 10 degrees [7-10].
Figure 5 shows different direction and tilt angle and the proportional amount of light intensity received on each
surface panel in comparison to an optimum of 30o and facing south.
Fig 5. different tilt and orientation and the amount of light intensity received
CONCLUSION
Performance of solar cells is dependent on operation conditions and their output parameters such as output
voltage, current, power, and fill factor vary with changes in temperature and light intensity. Also the location,
orientation and tilt of panel has significant role in the electrical characteristic of panel. Experimental results
showed that reduction in the open-circuit voltage for silicon solar cells is about 2.2mV/°C. The short-circuit current
increases slightly with temperature, for silicon solar cell this is about 0.0006 mA/°C. FF decreases with increasing
temperature this is approximated by 0.0015 per centigrade. Also the effect of temperature on the maximum power
output is menus 0.005 mw/°C.
According to results, short circuit current is directly proportional to the light intensity, while, open circuit
voltage changes logarithmically with light intensity.
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Ext J App Sci., 3 (2): 39-43, 2015
The photovoltaic solar panels must be oriented facing south in the northern hemisphere and facing north
southern hemisphere. Also Tilt of panels should be equal to the latitude minus 10 degrees. To increase the
efficiency of solar panels, it is better the solar panels are installed on a tracking system that follows the position
of the sun for to get a more light intensity.
ACKNOWLEDGEMENTS
The authors acknowledge the supports given by Sama technical and vocational training college of Parsabad
Moghan Branch for technical assistance in the experimental work.
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